System for clamping heat sink

ABSTRACT

A system for clamping a heat sink that prevents excessive clamping force is provided. The system may include a heat sink, a semiconductor device, a printed circuit) board, and a cover. The semiconductor device may be mounted onto the circuit board and attached to the cover. The heat sink may be designed to interface with the semiconductor device to transfer heat away from the semiconductor device and dissipate the heat into the environment. Accordingly, the heat sink may be clamped into a tight mechanical connection with the semiconductor device to minimize thermal resistance between the semiconductor device and the heat sink. To prevent excessive clamping force from damaging the semiconductor device, loading columns may extend between the cover and the heat sink.

BACKGROUND OF THE INVENTION

1. Technical Field.

The present invention is generally related to a system for clamping aheat sink. More specifically, the invention relates to a system forclamping a heat sink that prevents excessive clamping force.

2. Related Art.

When performing various functions, integrated circuits tend to generateheat. The integrated circuit may be cooled by dissipating heat into thesurrounding environment. Particularly in the audio electronics industry,the market has required manufacturers to provide smaller electronicpackages along with improved audio performance and power. To improveheat dissipation, heat sinks or blocks of metal may be connected withsemiconductor devices to conduct heat away from the semiconductor deviceand provide a larger surface area from which to dissipate the heat. Theheat sink often include fins to increase the surface area for heatdissipation and may even include a channel that provides fluid cooling.This may be particularly important with regard to power amplifiers andaudio circuits, as they can generate a significant amount of heat andmay require cooling to maintain audio performance of the electroniccomponent.

When attaching a heat sink to the semiconductor device, it may beimportant to have a tight mechanical coupling of the surface of the heatsink with the surface of the semiconductor device to minimize thermalresistance when transferring heat from the semiconductor device to theheat sink. Often, the components must be securely attached in a mannerthat will withstand harsh vibration and shock. For example, harsh shockand vibration are often encountered in an automotive audio environment.However, clamping the semiconductor device with excessive force cancause damage to the semiconductor device. Accordingly, there is a needto control the force used in securely clamping a heat sink to asemiconductor device.

SUMMARY

This invention provides a system for clamping a heat sink that preventsexcessive clamping force. The system may include a heat sink, asemiconductor device, a printed circuit board, and a cover. Thesemiconductor device may be mounted onto the circuit board and attachedto the cover. The heat sink may be designed to interface with thesemiconductor device to transfer heat away from the semiconductor deviceand dissipate the heat into the environment. Accordingly, the heat sinkmay be clamped into a tight mechanical connection to minimize thermalresistance between the semiconductor device and the heat sink.

The clamping may be accomplished using bolts that are inserted throughopenings in the cover and threaded into the heat sink. Tightening thebolts may apply a clamping force that presses the heat sink against thesemiconductor device. To prevent excessive clamping force from damagingthe semiconductor device, loading columns may extend between the coverand the heat sink. The loading columns serve as a stop or structuralsupport that act against the clamping force when the bolts are torqued.In addition, a button may be formed in the cover beneath thesemiconductor device to act as a support for the semiconductor device.Further, a teardrop shaped support may be formed in the cover to supportthe printed circuit board. The teardrop shaped support may include ahead portion with bolt openings and a tail portion that extends towardthe semiconductor device to support the printed circuit board.

Other systems, methods, features and advantages of the invention willbe, or will become, apparent to one with skill in the art uponexamination of the following figures and detailed description. It isintended that all such additional systems, methods, features andadvantages be included within this description, be within the scope ofthe invention, and be protected by the following claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be better understood with reference to the followingdrawings and description. The components in the figures are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention. Moreover, in the figures, likereferenced numerals designate corresponding parts throughout thedifferent views.

FIG. 1 is a sectional front view of a system for clamping a heat sink.

FIG. 2 is a sectional side view of a system for clamping a heat sink.

FIG. 3 is a perspective view of a cover for an electronic assembly.

FIG. 4 is a top plan view of a cover for an electronic assembly.

FIG. 5 is a sectional front view of the cover in FIG. 4.

FIG. 6 is a flowchart illustrating a method for clamping a heat sink.

FIG. 7 is a sectional front view of another embodiment of a system forclamping a heat sink.

FIG. 8 is another sectional front view of yet another embodiment of asystem for clamping a heat sink.

FIG. 9 is another sectional front view of yet another embodiment of asystem for clamping a heat sink.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1, an example of an electronic assembly 10 is provided. Theelectronic assembly 10 may include a semiconductor device 12, a circuitboard 14, a heat sink 18 and a cover 16. The semiconductor device 12 maybe in the form of a power amplifier or other semiconductor device thatgenerates heat during usage. These devices often include a ceramiccasing and metal pins or pads for facilitating electrical connection.One such device may be the TDA8594J amplifier from PHILIPS electronics.Accordingly, the heat sink 18 may be provided to receive heat from thesemiconductor device 12. The heat sink 18 transfers heat away from thesemiconductor device 12 and provides an increased surface area allowingimproved dissipation of the heat into the environment of the electronicassembly 10.

The electronic assembly 10 may also include a circuit board 14 such as aprinted circuit board to which the semiconductor device 12 may bemounted. The circuit board 14 may be made of a plastic and may includemetal traces that may be coupled to the semiconductor device 12. Thetraces may provide electrical power as well as data signals, such asaudio data signals, and/or control signals to the semiconductor device12 for processing. In addition, the circuit board 14 may includeadditional traces for communicating output signals, such as audiosignals, to other components or a speaker system after processing. Acover 16 extends around and protects the circuit board 14 andsemiconductor device 12. The cover 16 may be formed from a metal sheet,for example, through a series of forming or stamping events. The covermay be made of from any rigid material such as a steel or other metal,although the cover may also be made from other deformable materials suchas plastic or a fibrous material. The cover may include a corrosionresistant plating. For example, the cover can be made of a steel sheetwith a thickness of 1.0 mm and including a zinc coating. The cover 16includes loading columns 24 that extend from an outer surface of thecover through a hole in the circuit board 14 toward the heat sink 18.The loading columns 24 prevent the application of excessive clampingforce on the heat sink 18. As such, the loading columns 24 providestructural support to the heat sink 18 and prevent damage to thesemiconductor device 12.

The heat sink 18 may be clamped to the semiconductor device 12 using afastener 20. In FIGS. 1 and 2, the fastener 20 is shown as a bolt thatmay be threaded into a bore 22 formed in the heat sink 18. Accordingly,the fastener 20 extends through an opening in the cover 16, continuesthrough an opening in the circuit board 14, and engages the heat sink18. As mentioned, the fastener 20 may engage the heat sink 18 through athreaded engagement. Screws, rivets, clamps or any other fasteners mayalso be readily used. In the bolt arrangement shown, providing increasedtorque on the fastener 20 generates additional clamping forces bycompressing the semiconductor device 12 between the heat sink 18 and thecover 16. As shown in FIG. 1, the loading columns 24 and fastenerarrangement may be provided at multiple locations around thesemiconductor device 12, for example on the opposite sides of thesemiconductor device 12 to securely balance compression of the heat sink18 against the semiconductor device 12. The columns 24 may extendslightly above the semiconductor device 12 requiring compression of thecolumns 24. Alternatively, the columns 24 may extend flush with or belowthe semiconductor device 12. Similarly, the columns 24 may all be thesame length or may be different lengths thereby providing additionalsupport as the compression increases. In addition, a button 28 may beformed in the cover 16 to act as a spring between the cover 16 and thesemiconductor device 12 to absorb forces that may otherwise overcompress the semiconductor device 12. Further, the button 28 may have arounded or generally dome shape causing the bend of the sheet metal toact as a deformable spring. Further, the button 28 may include a flattop surface that reacts with the semiconductor device 12 through theprinted circuit board 14. As such, the cover 16 forms a planar surfaceand a button 28 extends from the planar surface and forms a secondplanar surface parallel to the first planar surface that reacts with thesemiconductor device 12. Further, the loading columns 24 also extendfrom the planar surface and may be formed substantially perpendicular toa planar surface. It is also understood that other deformable springsfor example, leaf springs or coil springs may be used in place of thebutton 28 to absorb forces. However, the button 28 may be integrallyformed in the cover 16. As may further be seen in FIG. 2, the heat sink18 may include fins 32 extending away from the semiconductor device 12providing additional surface area to improve heat dissipation throughconvection cooling. In addition, the fastener 20 may be located in achannel 30 formed in the cover 16.

In FIGS. 3, 4 and 5, additional views of the cover 16 from FIG. 2 areprovided. The cover 16 may extend along and around the printed circuitboard 14 and may include cooling holes 50 allowing for the flow of airfor convection cooling of the heat sink 18, semiconductor device 12, andthe circuit board 14. The cover 16 may interface with another housingportion that forms part of the heat sink 18 (seen in FIG. 2). The cover16 may surround and protect the components of the electronic assemblyincluding the circuit board 14 and the semiconductor device 12. Thecover 16 may be formed of a metal sheet through various stamping andforming processes. The trench 30 may be formed across the cover and maybe used for housing multiple semiconductor devices, for example a pairof power amplifiers. The button 28 may be stamped into the cover forminga rounded domed configuration including a flattened top surfaceproviding a more stable mechanical interface. The button 28, asdescribed previously, may act as a spring against semiconductor device12 to absorb the clamping force. In a similar manner, the loadingcolumns 24 may be stamped into cover 16 and bent perpendicular to a topsurface of the trench 30 to absorb additional clamping force and preventover clamping of the heat sink 18 and damage to the semiconductor device12. In addition, a recess 42 may be formed in the cover 16 forsupporting the circuit board 14 and distributing the force from thefastener 20 across the circuit board 14. The recess 42 may extend fromthe planar surface of the cover 16 toward the circuit board 14. Therecess 42 may include a flat surface parallel to the planar surface thatis elongated and extends towards the middle of the semiconductor device12 to provide additional support for the semiconductor device 12. Assuch, the recess 42 may have a generally teardrop shape with the head ofthe teardrop surrounding the fastener opening 44 and the tail of theteardrop extending towards the middle of the semiconductor device 12.This configuration may be mirrored on the opposite side of the cover 16as denoted by recess 46 and fastener opening 48, symmetrically forming agenerally teardrop shape with the tail extending towards thesemiconductor device 12. Other shapes for the recess may also be used,such as ovals or polygons, however the teardrop shape may provideimproved support due to support by the head of the screw on one end andthe converging tail lines on the opposite end. Although the cover 12, asshown in FIGS. 3-5, is configured to accommodate two semiconductordevices, it is readily understood that multiple additional semiconductordevices could be accommodated by duplicating this arrangement in variousadditional locations along the cover 16. Alternatively, a singlesemiconductor device may be accommodated in a single location on thecover 16.

In FIG. 6, an example method 100 is provided for clamping a heat sink 18to a semiconductor device 12. The method starts in block 101. The cover16 may be formed from a sheet of metal through various stampingoperations. In block 102, one or more columns 24 may be formed in asurface of the cover 16. At this stage, the column(s) 24 may resemble astrip parallel with the surface extending into an opening formed in thesurface of the sheet. In block 104, a button 28 may be formed in thesurface of the sheet at a semiconductor device location. Further, if twocolumns are used, the columns 24 may be juxtaposed and the button 28 maybe formed in between the two columns 24. The button 28 may be formed bystamping a portion of the surface into a dome shape. Alternatively,slits may be stamped in the surface and a portion of the surface betweenthe slits may be bent and/or stretched outwardly into a curved shape.Further, the top of the button may be formed into a flat surface that isconfigured to interface with a surface of the circuit board 14 orsemiconductor device 12. In block 106, teardrop shape supports 42 may beformed in the surface of the cover. Openings 44 may be formed in thecover 16 to be aligned with the teardrop shape supports 42 as denoted byblock 108. In block 110, a trench 30 may be formed in the surface of thecover 16 such that the columns 24, the button 28, and the supports 42are located in the trench and generally protected by other extendedsurfaces of the cover 16. In block 112, the columns may be bent suchthat columns 24 extend away from the surface of the cover 16. Forexample, the columns 24 may extend at approximately a 90° angle withrespect to the surface of the cover 16 allowing the columns 24 to extendbetween the surface of the cover 16 and the heat sink 18 during laterassembly steps. The semiconductor device 12 may be attached to a circuitboard 14 as denoted in block 114. In block 116, a circuit board 14 maybe attached to the cover 16 such that the columns 24 extend through thecircuit board 14 upwardly around the semiconductor device 12. The heatsink 18 may be attached to the semiconductor device 12 such that thecolumns 24 extend between the cover 16 and the heat sink 18 as denotedby block 118. The heat sink 18 may be attached to the semiconductordevice 12 utilizing fasteners 20 such as bolts that extend throughopenings 42 in the cover 16 and thread into the heat sink 18. When thebolts 20 are tightened, the columns 24 provide a structural supportacting to relieve the clamping force against the semiconductor device12. In this configuration, the button 28 and the teardrop shape supports42 serve to support the circuit board 14 and semiconductor device 12thereby reducing flex or stress imposed upon the assembly. The end ofthe method is denoted by block 120.

In FIG. 7, another example of an electronic assembly 210 is provided.The electronic assembly 210 may include a semiconductor device 212, acircuit board 214, a heat sink 218, and a cover 216. The heat sink 218may be provided to receive heat from the semiconductor device 212. Theelectronic assembly 210 may also include a circuit board 214 such as aprinted circuit board to which the semiconductor device 212 may bemounted. Traces on the circuit board 214 may provide electrical power aswell as data signals and/or control signals to the semiconductor device212. A cover 216 extends about and protects a circuit board 214 and thesemiconductor device 212. The cover 216 may be formed from a sheet metalfor example, through a series of forming or stamping events. The covermay be made from any rigid material, for example metal, plastic, orother similar material. The heat sink 218 may be clamped to thesemiconductor device 212 using a fastener 220. The fastener 220 is shownas a bolt. Although the fastener 220 may be threaded into the heat sink218 as depicted in FIG. 1, alternatively, in any of the embodimentsdiscussed, the fastener 220 may pass through a bore 222 in the heat sink218 and be threaded into the cover 216. Alternatively, the fastener 220may extend through the cover 216 and be threaded into a nut on anopposite side of the cover 216 from the heat sink 218.

The heat sink 218 may include columns 224 that extend around thesemiconductor device 212 to absorb force from over clamping of the heatsink 218 by the fasteners 220. In other alternative embodiments, thecolumns may be independent spacers extending between the cover and theheat sink. The columns 224 may extend through openings 226 in thecircuit board 214 to contact the cover 216. In particular, the columns224 may contact buttons 270 formed in the cover 216 that also act toabsorb over clamping of the heat sink 218. Buttons 270 may include afirst segment 252 of the cover 216 that extends angularly towards theheat sink 218 with respect to a planar region 250 of the cover that isgenerally parallel to the heat sink 218. The button 270 forms a topsurface 254 that is substantially parallel to the planar region 250 andaligned to interact with the column 224 of the heat sink 218. Similar tothe first segment 252, button includes a second segment 256 that isangularly formed with respect to the planar region 250 and that extendsbetween the top surface 254 and the planar region 250 thereby formingthe button 270.

The cover 216 may also also include a button 228 aligned with the centerof the semiconductor device 212. The button 228 may be surrounded by aplanar region 250 of the cover 216. The button 228 may include a firstsegment 230 that extends angularly away from the integrated circuit 212and that is connected to a planar portion 232 that is substantiallyparallel to the planar portion 250 of the cover 216. The planar portion232 may be connected to a second segment 336 that extends angularlytoward the semiconductor device 212, between the planar portion 232 anda planar surface 238. The planar surface 238 may be substantiallyparallel to the planar region 250 of the cover 216, as well as, thecircuit board 214 and the semiconductor device 212. Accordingly, thesurface 238 is configured to interact with the circuit board 214 or thesemiconductor device 212 through the circuit board 214. In addition, itcan be readily understood that the surface 238 may directly support thesemiconductor device 212 as described in other embodiments providedbelow. The first segment 230 and the second segment 236 may cause a gap234 to be formed between the cover 216 and the circuit board 214.Similarly, a third segment 240 may extend angularly between the planarsurface 238 and a planar segment 244 that is substantially parallel tothe planar region 250, similar to segment 232. A fourth segment 246extends between the planar segment 242 and the planar region 250 forminga gap 244 between the cover 216 and the circuit board 214, similar togap 234. The segments of the button 228 act together as a deformablespring to absorb any over clamping force and prevent damage to thesemiconductor device 212.

In FIG. 8, another example of an electronic assembly 310 is provided.The electronic assembly 310 may include a semiconductor device 312, aheat sink 318, and a cover 316. The heat sink 318 may be provided toreceive heat from the semiconductor device 312. A cover 316 may extendabout and protect the semiconductor device 312. The cover 316 may beformed from a metal sheet, for example, through a series of forming orstamping events. The cover 316 may be made from any rigid material, forexample metal, plastic, or other similar material. The heat sink 318 maybe clamped to the semiconductor device 312 using a fastener 320. Thefastener 320 is shown as a bolt that may be threaded into a bore 322formed in the heat sink 318. Accordingly, the fastener 320 extendsthrough an opening in the cover 316 and engages the heat sink 318. Asmentioned, the fastener 320 may engage the heat sink 318 through athreaded engagement. Screws, rivets, clamps or any other fasteners mayreadily be used. In the bolt arrangement shown, providing increasedtorque on the fastener 320 generates additional clamping forces bycompressing the semiconductor device 312 between the heat sink 318 andthe cover 316.

Loading columns 324 may extend from the cover 316 toward the heat sink318 to absorb compression force if the semiconductor device 312 is covercompressed. The loading columns 324 and fastener arrangement may beprovided at multiple locations around the semiconductor device 312, forexample on the opposite sides of the semiconductor device 312 tosecurely balance compression of the heat sink 318 against thesemiconductor device 312. In addition, a button 328 may be formed in thecover 316 to act as a spring between the cover 316 and the semiconductordevice 312 to absorb forces that may otherwise over compress thesemiconductor device 312. Further, the button 328 may have a rounded orgenerally dome shape causing the bend of the sheet metal to act as adeformable spring. Further, the button 328 may include a flat topsurface that contacts the semiconductor device 312. As such, the cover316 forms a planar surface and a button 328 extends from the planarsurface and forms a second planar surface parallel to the first planarsurface that reacts with the semiconductor device 312. Further, theloading columns 324 also extend from the planar surface and may beformed substantially perpendicular to a planar surface. It is alsounderstood that other deformable springs for example, leaf springs orcoil springs may be used in place of the button 328 to absorb forces.However, the button 328 may be integrally formed in the cover 316. Thebutton 328 may act as a deformable spring to absorb any over clampingforce and prevent damage to the semiconductor device 312.

In FIG. 9, another example of an electronic assembly 410 is provided.The electronic assembly 410 may include a semiconductor device 412, afirst heat sink 418, a second heat sink 414, and a cover 416. The firstand second heat sink 418 and 414 may be provided to receive heat fromthe semiconductor device 412. A cover 416 may extend about and protectthe semiconductor device 412. The cover 416 may be formed from a metalsheet, for example, through a series of forming or stamping events. Thecover 416 may be made from any rigid material, for example metal,plastic, or other similar material. The first and second heat sink 418,414 may be clamped to the semiconductor device 412 using a fastener 420.The fastener 420 is shown as a bolt that may extend through the firstheat sink 418 and be threaded into a bore 422 formed in the second heatsink 414. Accordingly, the fastener 420 extends through an opening inthe cover 416 and engages the second heat sink 414. In the boltarrangement shown, providing increased torque on the fastener 420generates additional clamping forces by compressing the semiconductordevice 412 between the first and second heat sink 418, 414.

Loading columns 424 may extend from the cover 416 toward the heat sink418 to absorb compression force if the semiconductor device 412 is covercompressed. The loading columns 424 and fastener arrangement may beprovided at multiple locations around the semiconductor device 412, forexample on the opposite sides of the semiconductor device 412 tosecurely balance compression of the heat sink 418 against thesemiconductor device 412. In addition, a button 428 may be formed in thecover 416 to act as a spring between the cover 416 and the semiconductordevice 412 to absorb forces that may otherwise over compress thesemiconductor device 412. Further, the button 428 may have a rounded orgenerally dome shape causing the bend of the sheet metal to act as adeformable spring. Further, the button 428 may include a flat topsurface that reacts with the semiconductor device 412 through theprinted circuit board 414. As such, the cover 416 forms a planar surfaceand a button 428 extends from the planar surface and forms a secondplanar surface parallel to the first planar surface that reacts with thesemiconductor device 412. Further, the loading columns 424 also extendfrom the planar surface and may be formed substantially perpendicular toa planar surface. It is also understood that other deformable springsfor example, leaf springs or coil springs may be used in place of thebutton 428 to absorb forces. However, the button 428 may be integrallyformed in the cover 416. The button 428 may act as a deformable springto absorb any over clamping force and prevent damage to thesemiconductor device 412.

While various embodiments of the invention have been described, it willbe apparent to those of ordinary skill in the art that many moreembodiments and implementations are possible within the scope of theinvention. Accordingly, the invention is not to be restricted except inlight of the attached claims and their equivalents.

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 20. A methodfor clamping a heat sink, the method comprising: forming columns in asurface of a cover that extend away from the surface; positioning acircuit board that includes a semiconductor device adjacent to the coversuch that the columns extend past the circuit board adjacent to thesemiconductor device; positioning a heat sink to be in contact with thesemiconductor device such that columns extend between the cover and theheat sink; and clamping the semiconductor between the cover and the heatsink.
 21. The method according to claim 20, further comprising:extending a fastener through the cover and engaging the heat sink toprovide a clamping force between the heat sink and the cover.
 22. Themethod according to claim 20, where the fastener is a bolt, and thecolumns are configured to prevent excessive clamping.
 23. The methodaccording to claim 20, further comprising the step of forming a buttonin the surface of the cover in a location proximate the semiconductordevice.
 24. The method according to claim 20, further comprising forminga teardrop shaped recess in the surface of the cover.
 25. The methodaccording to claim 24, where forming a teardrop shaped recess furthercomprises the step of forming an opening in the cover aligned with theteardrop shaped recess.
 26. The method according to claim 20, furthercomprising forming a trench in the surface of the cover.
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